This invention relates in general to a liquid crystal display device, and more particularly to a liquid crystal display device comprising a first and a second substrate, being manufactured in a flexible material, and a liquid crystal material being disposed between said substrates.
There is today a fast growing market for different kinds of displays utilising liquid crystal technology. Most of these displays comprise two plane substrates, commonly fabricated by a rigid glass material, and a layer of a liquid crystal material, arranged in-between said substrates. The glass substrates are separated from each other by equally sized spacers being positioned between the substrates, thereby creating a more or less uniform gap between the substrates. Further, electrode means for creating an electric field over the liquid crystal material are provided and the substrate assembly is then placed between crossed polarizers to create a display. Thereby, optical changes in the liquid crystal display may be created by applying a voltage to the electrode means, whereby the optical properties of the liquid crystal material disposed between the electrodes is alterable.
However, a problem with this kind of display is that they, due to the glass substrates, are quite rigid, heavy and exhibit a very low tolerance for bending stresses. Under bending moments the display tends to lose its image over a large area, due to the fact that the gap between the substrates changes, thereby causing the liquid crystal material to flow away from the bending area, resulting in a changed crystal layer thickness. Further, as glass is a fragile material, there is also a risk for breakage. A further disadvantage with using glass substrates is a complicated manufacturing procedure, due to the fact that the glass substrates must be handled with great delicacy.
Consequently, displays utilising glass substrates are less suitable, when a more flexible or even bendable display is desired.
Some efforts have been made in the field of exchanging the above described glass substrates with substrates of a less fragile material, such as plastic. Plastic substrates provide for lighter and less fragile displays. One display using plastic substrates are described in the patent document U.S. Pat. No. 5,399,390. However, the natural flexibility of the plastic substrates presents problems, when trying to manufacture liquid crystal displays in a traditional manner. For example, the spacing between the substrates must be carefully monitored in order to provide a display with good picture reproduction. An aim in the production of prior art displays utilising plastic substrates has therefor been to make the construction as rigid as possible, more or less imitating glass substrates. Thereby the flexible properties of the substrates have not been utilised to the full extent.
Therefore, one object of the present invention is to overcome the above-mentioned problems with the prior art, and to provide an improved liquid crystal display being flexible.
These and other objects are accomplished with a liquid crystal display device comprising a first and a second substrate, being manufactured in a flexible material, and liquid crystal material being disposed between said substrates, whereby said display device is characterised in that said substrates together form an array of cell enclosures, each containing an amount of liquid crystal material, whereby each of said cell enclosures is separated from the adjacent enclosures by intermediate flexible parts. By creating a display from a flexible material, and subdivide the display into a plurality of cell enclosures, and separating the enclosures from each other by flexible intermediate areas, a flexible, bendable display is created. Due to the configuration a bending moment on the display will cause a bending along an intermediate part rather than through a liquid crystal filled cell, thereby maintaining the display quality, since the cells or xe2x80x9cpixelsxe2x80x9d of the display are left intact. If, however, bending should cause deformation of one or more cells along a bending path, the loss of display quality will still be local, due to the separate enclosures, thereby maintaining the picture over a large area of the display.
Preferably, said first and second substrates are constituted by a first and a second polymeric sheet, respectively, said substrates being brought together in contact areas, together forming a grid-like pattern, whereby said cell enclosures are formed between said contact areas. This construction enables easy manufacturing, in which a layer of liquid crystal is sandwiched between two sheets of a flexible polymeric material. Thereafter, an array of enclosures is formed by creating a grid-like pattern of contact between the two sheets. The contact areas may be joined by melting, gluing or the like.
Further, the interior of each cell enclosure is suitably isolated from the interior of the surrounding enclosures. Thereby liquid crystal escape to neighbouring cells as a result of flexing or bending is prevented, and thereby any picture distortion caused by flexing may be limited to a rather confined area of the display.
Preferably, said cell enclosures is filled with a liquid crystal material, so as to establish an inner pressure in each cell in order to maintain the cell shape. By using the inner pressure to maintain the shape of the enclosure, and thereby the local distance between the enclosure substrates in each cell, the need for spacers is terminated. By using the inner pressure of each cell to maintain the distance between the substrates, bending of the display is less probable to cause cell distortions, as flexing movements are easily taken up by the flexible intermediate parts between said cells.
Suitably, electrode structures and/or polarizer structures are printed directly onto the substrate, which results in easy manufacturing and mounting, since the number of separate components is reduced.
Finally, said cell enclosures are essentially rectangular and equally sized in order to provide a pixel pattern and in order to maximise the active cell area of the display.